In the processing of molten metal in a furnace it is often desired to provide gas such as oxygen into the molten metal. A recent significant advancement for molten metal processing in an electric arc furnace is the post combustion method disclosed and claimed in U.S. Pat. No. 5,572,544--Mathur et al., wherein main oxygen is provided into the molten metal from above the surface of the molten metal pool, and post combustion oxygen is provided into the furnace above but close to the surface of molten metal pool. In such a system, because the main oxygen must penetrate into the molten metal pool, it must be injected into the furnace very close to the molten metal surface using one or more water cooled lances or injected into the molten metal at a point below the surface of the molten metal pool using one or more pipes. However, this expediency is still not satisfactory because the proximity of the tip of the gas injection device to the liquid surface causes excessive but unavoidable wear to the water cooled lance type oxygen injector. Pipes must be continually advanced to compensate for melting and oxidation of the end immersed in the molten steel bath which not only requires pipe manipulating equipment but also is expensive due to continual loss of pipe. Moreover, since the surface of the molten metal is not stationary, the oxygen injector must be continually moved to ensure that the oxygen injection is done at the proper location and with the proper nozzle to molten metal pool surface distance.
Accordingly, it is an object of this invention to provide a system for providing gas such as oxygen into a furnace containing a pool of molten metal wherein the gas passes into the molten metal pool, but excessive wear to the gas injection system is avoided.
There are times when it is desired to provide heat into a molten metal furnace, for example to melt scrap, in addition to providing gas into the molten metal pool. Accordingly, it is another object of this invention to provide a system for providing gas into a furnace so that the gas may be passed effectively into molten metal within the furnace while also providing heat into the furnace.
In the operation of an electric arc furnace it is desirable to generate a foamy slag layer above the molten metal pool. Accordingly it is a further object of this invention to provide a system for providing gas into an electric arc furnace so that the gas may be passed effectively into molten metal within the furnace while also generating a foamy slag above the molten metal.
In the operation of an electric arc furnace it is desirable to reduce the amount of fume which is generated. Accordingly, it is a further object of this invention to provide a system for providing gas into an electric arc furnace which minimizes the creation of splash and further provides a reducing atmosphere in the vicinity of the splash that does form to reduce the amount of fume formation.
In the operation of an electric arc furnace it is desirable to inject reagents such as carbon, lime, alloys, etc. in powder form into the bath. Accordingly, it is a further object of this invention to provide a system for providing gas into an electric arc furnace so that the gas may be passed effectively into molten metal within the furnace while also introducing powdered reagents into the molten metal.